Heat exchanger, tube for heat exchanger, and method of manufacturing the heat exchanger and the tube

ABSTRACT

A heat exchanger ( 1 ) is formed by stacking tubes ( 2 ) formed by rolling a flat tube material ( 10 ) with a fin ( 3 ) interposed between the adjacent tubes, joining tanks ( 4 ), ( 5 ) and the tubes, ( 2 ) to appropriately communicate the tubes ( 2 ) and the tanks ( 4 ), ( 5 ), wherein the tube ( 2 ) is provided with a partition ( 22 ) for dividing a passage ( 6 ) of the tube ( 2 ) into passages ( 6 ),( 6 ) and the partition ( 22 ) has an extra section for absorbing a deformation produced when a partition part ( 30 ) and the tube are formed.

1. Technical Field

The present invention relates to a tube for a heat exchanger formed byrolling an aluminum material to provide a partition for dividing apassage, its production method and a heat exchanger using the tube.

2. Background Art

Conventionally, as a tube for a heat exchanger, there is known a flattube which is formed by rolling an aluminum material.

For example, a heat exchanger used for vehicles may be a combination ofat least two heat exchangers having different functions.

Among the tubes used for such heat exchangers, the tube described in,for example, Japanese Patent Laid-Open Publication No. 6-123571 or No.7-41331, is formed by having a partition which is formed to have anapproximately θ-shape cross section by bending an aluminum material inmultiple stages by rolling, and forming a plurality of passages in thetube by adhering the partition and a wall facing the partition bybrazing in an oven.

This type of tube for a heat exchanger is formed with the partitions inthe tube even though the number of step is relatively few, so thatrecently it is used as a tube for a heat exchanger used for arefrigeration cycle for cars.

The heat exchangers are becoming smaller in size with improvement oftheir performance. Therefore, an aluminum improvement of theirperformance. Therefore, an aluminum material having a less thickness ofabout 0.2 mm is being used for the tubes for the heat exchangers. Thesize of tube being used is made very small and thin with dimensions of awidth of about 15 mm and a height of about 1.5 mm.

A heat exchanger tube to be used for a compact heat exchanger isrequired to have an accuracy for the dimensional control when it isformed by rolling. Meanwhile, the formed tube has dimensional unevennessconcentrated on the neighborhood of the portion corresponding to theends of the tube material in the final sectional shape.

For example, when the tube is formed, a partition part is formed at endsof the tube material and the partition parts formed at both ends of thematerial are joined to form a partition. When the partition parts areformed at the ends of the tube material where unevenness tends to occurwhile the tube is being formed, a gap or the like is formed on the tube,and the dimensional control may become insufficient. And, brazing maybecome defective depending on a degree of unevenness produced. The tubefor a heat exchanger which has a defective brazing or the like has adefective pressure strength, or the right and left passages in the tubebecome non-uniform. Therefore, there is a problem that a defectivebypass is produced or leakage to outside occurs.

Therefore, it is an object of the present invention to provide a tubefor a heat exchanger which is produced while eliminating unevennesswhich could be caused in machining to form the tube, its productionmethod and a heat exchanger.

SUMMARY OF THE INVENTION

The invention described in claim 1 is a heat exchanger formed by rollinga flat tube material, forming tubes having a passage with at least oneend open, stacking the tubes with fins interposed between adjacenttubes, disposing tanks on the side of the passage openings of the tubes,joining the tanks and the tubes to appropriately communicate the tubesand the tanks, wherein the tubes are provided with a first flat section,first erected sections which are erected at about right angles from bothends of the first flat section, and a second flat section which iscontinuous from the first erected sections and substantially parallel tothe first flat section; partition parts are formed on the second flatsection by bending the ends of the second flat section; and thepartition parts are contacted with the first flat section to establish apartition for dividing the passage of the tubes.

The invention described in claim 2 is a tube for a heat exchanger whichis formed by rolling a flat tube material and has a passage with atleast one end open, wherein the tube is provided with a first flatsection, first erected sections which are erected at about right anglesfrom both ends of the first flat section, a second flat section which iscontinuous from the first erected sections and substantially parallel tothe first flat section, and a partition for dividing a tube passage; andthe partition is provided with partition parts formed by bending thetube material and an extra section for absorbing deformation, which isproduced when the tube is formed, as much as possible.

The invention described in claim 3 is the tube for a heat exchangeraccording to claim 2, wherein the extra section has a shape to cut intothe first flat section.

The invention described in claim 4 is the tube for a heat exchangeraccording to claim 2 or 3, wherein the extra section has a shape to cutinto the second flat section.

The tube used for a heat exchanger of the present invention is providedwith the partition in the passage of the tube for the heat exchangereven when it is formed of a thin material for use in a compact heatexchanger, so that a required pressure strength can be assured.

And, the partition of the tube for a heat exchanger absorbs unevenness,which is produced while machining, by the extra section as much aspossible. As a result, the formed tube for the heat exchanger isprevented from having a defective brazing and can hold the requiredpressure strength. The tube for the heat exchanger has the passagesequally divided by the partition and can prevent a defective passage orthe like in the tube. Therefore, it becomes possible to produce aquality heat exchanger.

And, when the extra section is formed in such a way to cut into thefirst flat section, the contacted portion of the partition parts and thefirst flat section becomes wide, the brazing property is improved, andthe partition parts and the first flat section are joined with goodwatertightness.

When the extra section is formed so to cut into the second flat section,the partition parts and the second flat section are joined with goodwatertightness.

The invention described in claim 5 is the tube for a heat exchangeraccording to claim 2, wherein the tube material has a size exceeding twotimes a vertical size of the partition in addition to a predeterminedmaterial size for forming the tube for a heat exchanger; and thepartition has partition parts which are formed to protrude from thesecond flat section by bending and joining the ends of the tube materialto form overlaid portions and bending a predetermined point of theoverlaid portions at about right angles and extra sections which arejoined along the second flat section.

When the extra section to be joined along the second flat section isprovided according to the present invention, the tube can keep theprecision of the tube shape because a deformation caused when the tubeis being produced can be absorbed as much as possible by the extrasection by the effect of sizing performed after or in the process offorming the tube.

The tube of the present invention has an improved pressure strength byforming the overlaid portion which has the ends of the tube materialbent and joined, forming the partition parts by bending the overlaidportion, and mutually contacting the partition parts to form thepartition. Therefore, the partition has a state that the tube materialis overlaid four times.

The invention described in claim 6 is a method of producing a tube for aheat exchanger which is formed by rolling a flat tube material andprovided with a partition for dividing a passage, wherein the tubematerial has a size exceeding two times a vertical size of the partitionin addition to a predetermined material size for forming the tube; themethod comprising a first step to form an overlaid portion by bending apredetermined portion of the ends of the tube material to substantially180 degrees and joining; a second step to form partition parts bybending a predetermined portion of the overlaid portion or apredetermined portion of the tube material to substantially 90 degreesand extra sections for absorbing deformation, which is caused when thetube is formed, as much as possible; and a third step to form the tubeby contacting the protruded ends of the partition parts to the firstflat section.

The invention described in claim 7 forms the extra sections which cutinto the first flat section in the first or second step of claim 6.

According to the method of producing the tube for a heat exchanger ofthe present invention, the contact portion between the partition partsand the first flat section becomes wide when the tube is formed becausethe extra section which cuts into the first flat section is formed, thebrazing property is improved, and the partition parts and the first flatsection are joined with good watertightness to form the tube.

The invention described in claim 8 forms the extra sections which cutinto the second flat section in the first or second step of claim 6 or7.

According to the method of producing the tube for a heat exchanger ofthe present invention, the partition parts and the second flat sectiondo not cause a gap and joined with good watertightness when the tube isformed because the extra section which cuts into the second flat sectionis formed.

The invention described in claim 9 is the invention according to claim6, wherein the first step includes a step to form the first bendingsection which becomes a bending fulcrum of the overlaid portion, and astep to form the second bending section which has an inner angle largerthan that of the first bending section.

The method of producing the tube for a heat exchanger of the presentinvention decreases the load applied to the first bending section andforms the overlaid section while keeping precision without causingdisplacement on the first bending section when the second bendingsection which has the inner angle larger than the inner angle of thefirst bending section is formed at the leading end of the first bendingsection which is the bending fulcrum and the overlaid portion which hasthe ends of the tube material bent and joined is formed.

The invention described in claim 10 is the invention according to anyone of claims 6 to 9, wherein the third step is provided with a step tocorrect unevenness in precision when the tube is formed by deformingunevenness.

According to the method of producing the tube for a heat exchanger ofthe present invention, unevenness in precision caused when the tube isformed is absorbed for correction by the extra section or the like, anda quality product with precision can be formed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a heat exchanger partly broken awayaccording to an embodiment of the present invention;

FIG. 2 is an enlarged diagram showing a connected portion of the tubesand the tanks shown in FIG. 1 according to the embodiment of theinvention;

FIG. 3 is an enlarged diagram showing the vicinity of a partition of atube for a heat exchanger according to the embodiment of the invention;

FIG. 4 is a diagram showing an end surface of a tube for a heatexchanger according to another embodiment of the invention;

FIG. 5 is a diagram showing a state that an overlaid portion is formedat an end of a tube material;

FIG. 6 is an explanatory diagram schematically showing a process ofbending a first bending section, which is formed at either end of a tubematerial, at an inner angle of 120 degrees according to the embodimentof the invention;

FIG. 7 is an explanatory diagram schematically showing a process ofbending the first bending section, which is formed at either end of thetube material, at an inner angle of 90 degrees;

FIG. 8 is an explanatory diagram schematically showing a process ofbending the first bending section, which is formed at either end of thetube material, at an inner angle of about 40 to 80 degrees;

FIG. 9 is an explanatory diagram schematically showing a process offorming a second bending section at the leading end of the first bendingsection to be formed at the ends of the tube material;

FIG. 10 is an enlarged diagram showing the first and second bendingsections shown in FIG. 9:

FIG. 11 is an explanatory diagram showing vectors of a load applied tothe first bending section when an overlaid portion is formed by formingthe second bending section and bending it at about 180 degrees with thefirst bending section as a fulcrum;

FIG. 12 is an explanatory diagram showing vectors of a load applied tothe first bending section when an overlaid portion is formed by bendingat about 180 degrees with the first bending section as a fulcrum withoutforming the second bending section;

FIG. 13 is an enlarged diagram of an end portion of a tube material,showing an explanatory diagram schematically showing a process to form apartition part and an extra section by bending the overlaid portion;

FIG. 14 is an enlarged diagram of the end portion of the tube material,showing an explanatory diagram schematically showing a process to formthe partition part and the extra section by bending the overlaidportion;

FIG. 15 is an enlarged diagram of the end portion of the tube material,showing a process to size after the partition part and the extra sectionare formed;

FIG. 16 is a diagram showing a process to size after the partition partis formed when the extra portion is not formed; and

FIG. 17 is an explanatory diagram schematically showing a process toform a tube for a heat exchanger by roll molding of a flat tubematerial.

BEST MODE FOR CARRYING OUT THE PRESENT INVENTION

Embodiments of the present invention will be described with reference tothe accompanying drawings.

FIG. 1 shows an example of a heat exchanger 1. For example, the heatexchanger 1 is used as a heater core or a radiator of an airconditioning system for vehicles.

The heat exchanger 1 is formed by alternately stacking flat tubes 2 andcorrugated fins 3 into plural layers and bonding both ends of thestacked tubes 2 in the longitudinal direction to tanks 4, 5.

For example, the tubes 2 are formed of an aluminum material, such as analuminum alloy, having aluminum clad with a brazing material as a mainmaterial. The tubes 2 are provided with passages 6, 6 through which aheat-exchange medium flows as shown in FIG. 1 and FIG. 2. The passages6, 6 have an opening at either end in the longitudinal direction.

The tank 4 is provided with a supply pipe for supplying the medium tothe tank 4, and the other tank 5 is provided with a discharge pipe fordischarging the medium from the tank 5 (not shown).

The medium flows into the heat exchanger 1 through the supply pipe isheat-exchanged with the outside air by a heat-exchange function of thetubes 2 and fins 3 for a heat exchanger. After the heat exchange, themedium, which is condensed by the heat exchanger 1 when the heatexchanger 1 is a condenser, is discharged through the discharge pipe andcirculated through a heat exchange cycle.

As shown in FIG. 2, the tube 2 is configured by a first flat section 19which is substantially flat, first erected sections 20, 20 which arecontinuous from both ends of the first flat section 19 and have a nearlysemicircular shape, second flat sections 21, 21 which are continuousfrom the first erected sections, substantially parallel to the firstflat section 19 and have a size nearly half of the first flat section,and the passages 6, 6 which are divided by a partition 22 formed bycontacting partition parts 30, 30.

The partition part 30 is formed by bending ends of a flat tube material.As shown in FIG. 3, the partition part 30 is formed by forming a firstbending section 30 c with a predetermined point of the end of the tubematerial used as a fulcrum and forming a second bending section 30 d bybending at about right angles along the edge of the tube material.

Here, the partition part 30 is to have a portion 30 a which extends in adirection of the first flat section and a portion 30 b which extends ina direction of the second flat section. The portion 30 a extending inthe direction of the first flat section and the portion 30 b extendingin the direction of the second flat section are not necessarily formedto have the same dimension as a length between the first and second flatsections.

For example, when an extra section which has a size (Y) slightly longerthan a length (X) between the first and second flat sections is formedat the portion 30 a extending in the direction of the first flatsection, it becomes possible to make the first bending section 30 c tocut into the first flat section 19 by a predetermined value Z (e.g.,about 0.05 mm). Therefore, the partition part 30 improves a brazingproperty by expanding a portion to be contacted with the first flatsection 19 and can be joined to the first flat section 19 with goodwatertightness.

For example, when an extra section which has a size (Y) slightly longerthan a length (X) between the first and second flat sections is providedat the portion 30 b extending in the direction of the second flatsection, it becomes possible to make the edge of the tube material tocut into the second flat section 21 by a predetermined value W (e.g.,about 0.05 mm). Therefore, the partition part 30 can be joined with thesecond flat section 21 with good watertightness without forming a gap.

Thus, the partition part 30 can absorb unevenness in the length of thepartition part 30 as much as possible by virtue of the extra sectionwhich is formed at the portion 30 a extending in the direction of thefirst flat section and the portion 30 b extending in the direction ofthe second flat section. Therefore, the tube 2 does not cause a gap andimproves the brazing property. Since no gap or the like is formed at thepartition 22, a defective bypass or an external leakage is not caused.

Then, another embodiment of the tube 2 will be described. FIG. 4 is adiagram showing an end surface of the tube 2.

As shown in FIG. 4, the tube 2 has a partition 45 which divides thepassages 6, 6 at about the center of the tube 2.

A tube material 10 is bent and joined at about 180 degrees using apredetermined point of its end as a fulcrum to form an overlaid portionand a predetermined point of the overlaid portion is bent at about 90degrees to form a partition part 41 and an extra section 42. And, thetube 2 is configured to have the partition 45 which has both of thepartition parts 41, 41 formed at both ends of the tube material 10mutually contacted and a protruded end 41 a of the partition part 41contacted to the first flat section 19.

Then, a method of producing the tube 2 shown in FIG. 4 will bedescribed.

FIG. 5 to FIG. 17 are diagrams showing an end surface of the tubematerial or its part in respective steps to form the tube 2 shown inFIG. 4.

First, a first step to form an overlaid portion 40 will be described.FIG. 5 is a diagram showing a state that the overlaid portion 40 isformed at an end of the tube material 10.

The tube material 10 has a size of more than two times a size of thepartition 45 in addition to a predetermined material size for formingthe tube 2.

First, the tube material 10 is formed a first bending section 43 at itsboth ends. The first bending section 43 is formed by bending the tubematerial 10 using as a fulcrum a portion which can form the overlaidportion 40 having a size between the first and second flat sections 19,21, namely a size (S) exceeding a size (X) of the partition 45 (see FIG.3).

The first bending section 43 is formed by bending in such a way that afirst bending angle has an inner angle of about 120 degrees, bending insuch a way that a second bending angle has an inside angle of about 90degrees, and gradually bending in such a way that a third bending anglehas an inside angle of about 40 to 80 degrees as shown in FIG. 6 to FIG.8.

Thus, when the first bending section 43 is formed by gradually bending,unevenness which is produced when bending is reduced, and a load on thebending fulcrum of the first bending section 43 is decreased. Therefore,the heat-exchanger tube formed can maintain accuracy by the dimensionalcontrol.

The bending angle to form the first bending section 43 is not limited tothe aforementioned angle but can include a first bending angle of 90degrees or more, a second bending angle of 90 degrees or less and athird bending angle which is not larger than the second bending angle.

A curved portion 11 is formed at about the center of the tube material10 to protrude in a direction of forming the first bending section inorder to maintain accuracy of the tube 2 by absorbing deformation causedwhen the tube is formed, to be described later, by the curved portion11.

Then, a second bending section 44 which has an inner angle larger thanthat of the first bending section 43 is formed at the leading end of thefirst bending section 43 as shown in FIG. 9 and FIG. 10. It is assumedthat the second bending section 44 has an inner angle of 110 degrees,for example.

Specifically, it is assumed that the inner angle of the first bendingsection 43 is V1 and the inner angle of the second bending section 44 isV2, and the second bending section 44 is formed to have V1<V2.

The second bending section 44 is formed to avoid a problem that afulcrum is displaced and the bending section 43 has unevenness when theoverlaid portion 40 is formed by bending the end of the tube material ata single stroke.

Differences between the formation of the second bending section 44 andno formation of it will be described in the form of vectors.

FIG. 11 shows a load on the first bending section 43 when the secondbending section 44 is formed, as a vector sum E=e1+e2+e3+e4+e5.Meanwhile, FIG. 12 shows a load on a first bending section 43′ when thesecond bending section 44 is not formed, as a vector sumE′=e′1+e′2+e′3+e′4+e′5. When these two vector sums E, E′ are compared,it is obvious that they have a relation of E<E′.

Therefore, when the second bending section 44 is formed, the loadapplied to the bending section 43 becomes small and unevenness producedby the load is decreased, thereby keeping accuracy of the overlaidportion 40.

And, the second bending section 44 is pressed down and joined to formthe overlaid portion 40.

Then, a second step to form the partition part 41 and the extra section42 will be described. FIG. 13 and FIG. 14 are explanatory diagramsschematically showing steps to form the partition part 41 and the extrasection 42 from the overlaid portion 40.

The partition part 41 is formed by determining as a bending fulcrum aportion which satisfies a size between the first flat section 19 and thesecond flat section 21 of the overlaid portion 40, namely a portionsatisfying the partition 45, and bending at about right angles with thebending fulcrum at the center. The partition part 41 is a portionprotruded from the portion configuring the second flat section 21, andthe extra section 42 is a portion which is joined along the portionconfiguring the second flat section 21.

First, the overlaid portion 40 is bent at an inner angle of about 120degrees with the fulcrum at the center as shown in FIG. 13. Then, theoverlaid portion 40 is bent at an inner angle of about 90 degrees withthe fulcrum at the center to form the partition part 41 and the extrasection 42 as shown in FIG. 14. Then, sizing is performed to adjustdeviations in the size caused when the partition part 41 and the extrasection 42 are formed.

FIG. 15 is a diagram showing a sized state. The arrows in FIG. 15indicate a loading direction that a force is applied by sizing. Thebroken lines in FIG. 15 indicate the shapes of the partition part 41 andthe extra section 42 before sizing.

The force applied by sizing hits against the portion forming the secondflat section 21 and then applied in the direction of the extra section42 joined along the second flat section 21. Therefore, the extra section42 is deformed, and the size of the partition part 41 is accuratelycontrolled.

Meanwhile, FIG. 16 is a diagram showing that a gap is formed at aportion where a partition part 41′ and a second flat section 21′ areformed because the extra section 42 is not formed. As shown in FIG. 16,when the gap is formed between the partition part 41′ and the portionwhere the second flat section 21′ is formed, accurate dimensionalcontrol cannot be made even if the dimensional control is made by sizingbecause the force, which was applied when sizing, is relieved from theleading end of the partition part 41′.

Since the partition 45 of the tube 2 in this embodiment has the extrasection 42 joined along the second flat section 21, a sizing effect isfully produced, and accurate dimensional control can be made.

Therefore, when the partition 45 is formed by contacting both of thepartition parts 41, the passages 6, 6 of the heat-exchanger tube can bedivided equally by the partition 45, a defective flow in the tube is notcaused, and manufacturing of quality products becomes possible.

Lastly, a third step to form the tube 2 will be described. FIG. 17 is anexplanatory diagram schematically showing respective steps to form thetube 2 from the tube material 10 having the partition part 41.

First, predetermined portions where the first erected portions 20, 20 ofthe tube material 10 are formed are bent in order of (a), (b), (c) and(d) at about right angles in an upward direction in the drawing. Whenthe tube material 10 becomes about right angles, the tube material 10curved in the lower direction is restored to the original state asindicated by an arrow (f). And, from the state that the tube material 10has nearly right angles, a protruded section 41 a of the partition part41 is bent so to come into contact with about the center of the tubematerial 10. Two passages 6, 6 are formed through the above steps, andthe tube 2 is completed.

The tube 2 formed through the above first to third steps and the fin 3are alternately stacked, the open ends of the tube 2 are inserted intothe tube insertion holes of the tanks 4, 5 to temporarily assemble theheat exchanger, and the temporarily assembled heat exchanger is brazedin an oven. Thus, the tubes 2 and the tanks 4, 5 and also the tubes 2and the fins 3 are brazed to complete the heat exchanger 1.

According to the heat exchanger, the tube for the heat exchanger and itsproduction method of this embodiment, a good product can be producedwithout causing a defective brazing of the partition parts, defectivestrength or defective flow in the tube.

The partitions 22, 45 of the tube 2 for a heat exchanger according tothis embodiment are formed by folding the tube material four times, sothat brazing is improved, and a pressure strength is also improved.

Industrial Applicability

The heat exchanger, the tube for the heat exchanger and its productionmethod according to the invention are to remove unevenness caused inproducing the tube as much as possible, and particularly suitable for acompact heat exchanger or a tube used for the compact heat exchanger.

What is claimed is:
 1. A tube for a heat exchanger which is formed by rolling a flat tube material and has a passage with at least one end open, wherein: the tube is provided with a first flat section, first erected sections which are erected at about right angles from both ends of the first flat section, a second flat section which is continuous from the first erected sections and substantially parallel to the first flat section, and a partition for dividing a tube passage; the partition is provided with overlaid portion which are formed by bending and joining the ends of the tube material; the overlaid portion provided at one end of the tube material and the overlaid portion provided at the other end of the tube material are joined to form a partition part; the partition part includes extra sections at both ends of each overlaid portion; and the extra sections are joined with the first and second flat sections.
 2. A tube for a heat exchanger which is formed by rolling a flat tube material and has a passage with at least one end open, wherein: the tube is provided with a first flat section, first erected sections which are erected at about right angles from both ends of the first flat section, a second flat section which is continuous from the first erected sections and substantially parallel to the first flat section, and a partition for dividing a tube passage; the partition is provided with overlaid portion which are formed by bending and joining the ends of the tube material; the partition has a partition part formed by bending a predetermined point of the overlaid portions at about right angles to protrude from the second flat section, and extra sections joined along the second flat section; and the tube material has a size exceeding two times a vertical size of the partition in addition to a predetermined material size for forming the tube for a heat exchanger.
 3. A method of producing a tube for a heat exchanger which is formed by rolling a flat tube material and provided with a partition for dividing a passage, wherein the tube material has a size exceeding two times a vertical size of the partition in addition to a predetermined material size for forming the tube; the method comprising: a first step to form an overlaid portion by bending a predetermined portion of the ends of the tube material and joining them; a second step to form a partition part by bending a predetermined portion of the overlaid portion or a predetermined portion of the tube material to about 90 degrees, and an extra section for absorbing deformation which is caused during formation of the tube as much as possible; and a third step to form the tube by contacting a protruded end of the partition part; and wherein in the first or second step, an extra section which cuts into the first flat section or the second flat section is formed.
 4. The method of producing a tube for a heat exchanger according to claim 3 wherein the first step includes a step to form a first bending section which becomes a bending fulcrum of the overlaid portion, and a step to form a second bending section which has an inner angle larger than that of the first bending section. 